Polymeric films and bags

ABSTRACT

The present invention is directed to a method of incrementally stretching polymeric film formed from a blown film extrusion process. The present invention is further directed to a polymeric bag formed from an incrementally stretched polymeric film. The incremental stretching is performed on a collapsed polymeric bubble via a pair of intermeshing rollers. The incrementally stretched polymeric film may be stretched only along a portion of its width. The polymeric bag may be a drawstring trash bag with an extended hem where only the extended hem of the polymeric bag comprises incrementally stretched polymeric film.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to improvements in the construction andmanufacture of polymeric film and bags. In particular, the presentinvention relates to improvements in varying the thickness of filmformed from a blown film extrusion process and constructing polymericbags from the resultant film.

2. Description of the Related Art

Polymeric bags are ubiquitous in modern society and are available incountless combinations of varying capacities, thicknesses, dimensions,and colors. The bags are available for numerous applications includingtypical consumer applications such as long-term storage, food storage,and trash collection. Like many other consumer products, increaseddemand and new technology have driven innovations in polymeric bagsimproving the utility and performance of such bags. The presentinvention is an innovation of particular relevance to polymeric bagsused for trash collection.

Polymeric bags are manufactured from polymeric film produced using oneof several manufacturing techniques well-known in the art. The two mostcommon methods for manufacture of polymeric films are blown-filmextrusion and cast-film extrusion. In blown-film extrusion, theresulting film is tubular while cast-film extrusion produces a generallyplanar film. The present invention is generally applicable to drawstringtrash bags manufactured from a blown-film extrusion process resulting intubular film stock. Manufacturing methods for the production ofdrawstring bags from a web of material are shown in numerous prior artreferences including, but not limited to, U.S. Pat. Nos. 3,196,757 and4,624,654, which are hereby incorporated by reference.

In blown film extrusion, polymeric resin is fed into an extruder wherean extrusion screw pushes the resin through the extruder. The extrusionscrew compresses the resin, heating the resin into a molten state underhigh pressure. The molten, pressurized resin is fed through a blown filmextrusion die having an annular opening. As the molten material ispushed into and through the extrusion die, a polymeric film tube emergesfrom the outlet of the extrusion die.

The polymeric film tube is blown or expanded to a larger diameter byproviding a volume of air within the interior of the polymeric filmtube. The combination of the volume of air and the polymeric film tubeis commonly referred to as a bubble between the extrusion die and a setof nip rollers. As the polymeric film tube cools travelling upwardtoward the nip rollers, the polymeric film tube solidifies from a moltenstate to a solid state after it expands to its final diameter andthickness. Once the polymeric film tube is completely solidified, itpasses through the set of nip rollers and is collapsed into a collapsedpolymeric tube, also referred to as a collapsed bubble.

One common household item formed from the polymeric film produced by ablown film extrusion process are drawstring trash bags. Frequently,drawstring trash bags are used to line a rigid container, such as atrash can, for the disposal of household trash. When used with a rigidcontainer, it is common to fold the upper opening of a drawstring trashbag over the upper rim of the container to keep the upper opening of thebag accessible. Some rigid containers provide retaining devices to holdthe upper opening of a drawstring bag in place while, in otherinstances, the drawstring bag may provide certain features or propertiesthat facilitate keeping the bag in place on the container. The use ofthese rigid containers is particularly common in connection with13-gallon drawstring bags. Rigid containers may also be used with largerbags, such as those commonly used for the collection of outdoor or yardwaste. When drawstring bags are used with supporting rigid containers,the drawstring trash bag is often filled with trash and other debrisuntil the capacity of the container or trash bag is reached.

After filling the drawstring bag with trash or debris, the bag and itscontents are generally pulled out of the rigid container in one ofseveral ways. Some consumers may prefer to pull the drawstrings taut,using the drawstrings to pull the bag and its contents out of thecontainer. However, in many cases, consumers pull the bag out of therigid container before pulling the drawstrings taut. In such cases, aconsumer will typically grab the upper opening of the bag hem or, morecommonly, the area immediately below the hem. As the consumer grabs thebag and pulls it out of the container, significant force can result inthe area immediately below the hem. This force on the hem is due to theweight of the bag contents and the pulling action by the consumer, whichcan cause the polymeric film to puncture or fail in this region of thebag—especially when the contents of the bag are particularly heavy.Thus, there is a need to improve the strength and puncture resistance ofthe hem and the area immediately below the hem.

Another aspect of prior art drawstring bags that may be subject toimprovement is the tendency for the hems of drawstring bags to detach ifthere are even minor manufacturing defects. In particular, if thepressure or heat used to create the hem seal across the width of thedrawstring trash bag is too great, the integrity of the drawstring trashbag may be endangered due to crystallization of the polymeric film alongthe hem seal. In these cases, when the drawstring trash bag is filledwith trash or debris, the hem seal may fail causing the entire length ofthe hem, and the drawstring contained within the hem, to “zipper” ordetach from the rest of the bag. Thus, there is a need to improve therobustness of the hem seal to ensure that the drawstring is retainedabout the opening of the trash bag.

Another further improvement of prior art drawstring trash bags may be toreduce the cost of producing the trash bags. A substantial cost ofmanufacturing trash bags can be related to the cost of polymeric resinused to produce a bag. One way to decrease the cost of producing bags isto decrease the thickness of film used in their manufacture, whichreduces the amount of polymeric resin required to make a bag. However,reducing the thickness of film used to produce a bag can lead to areduction in the strength of the bag. Thus, a need exists to decreasethe use of resin to produce drawstring trash bags while maintainingenough strength so that the bags do not fail when used.

One method of thinning out the material of a bag is by incrementallystretching the film. Stretching the film incrementally allows stretchingthe film in only selected areas of the film. Incrementally stretchingalso provides for a ribbed pattern to be placed on the bag that mayserve to differentiate the appearance of the bag. The incrementalstretching can maintain the thickness of the bag in segments that arenot stretched that can be referred to as thick ribs. These thick ribsmay be perceived by an end user of the bag such that the bag isperceived to be as thick as the previously un-stretched film.

In the prior art, U.S. Pat. No. 4,116,892 to Schwarz discloses using apair of grooved intermeshing rollers to incrementally stretch anorientable polymeric material in a direction transverse to the machinedirection. In a related field, U.S. Pat. No. 5,041,255 to Zafirogludiscloses the use of a pair of intermeshing circumferentially ribbedrollers for stretching portions of a fibrous web.

In a much later publication, US Pat. Appl. Pub. 2012/0088645A1 disclosesuse of intermeshing rollers, each roller having a plurality of circularridges protruding outwards, to stretch a portion of a polymeric web in adirection transverse to the machine direction. The application furtherdiscloses that the use of the aforementioned intermeshing rollers can beused on the film so that the panels of the trash bag are imparted with aribbed pattern running in a lengthwise direction, parallel to thedirection that the film is extruded.

In light of the foregoing, it would be desirable to provide a means forreinforcing the drawstring trash bag in the area immediatelyadjacent/below the hem area of the trash bag while also controlling thethickness of the reinforced areas. It would also be desirable to provideadditional improvements to the manufacture of drawstrings bags bythinning out the bags in desirable locations to provide targetedstrengthening and light weighting of the bag. The present inventionrepresents a novel solution to address this needs.

SUMMARY OF THE INVENTION

In at least one embodiment of the invention, a master roll of polymericfilm for forming trash bags may be formed. To form the master roll, apolymeric film tube may be formed by a blown film extrusion process.Once the polymeric film tube is formed, it may be collapsed by a pair ofnip rollers to form a collapsed bubble. A pre-selected partial width ofthe collapsed bubble may be ring-rolled to form an incrementallystretched collapsed bubble. The incrementally stretched collapsed bubblemay be slit lengthwise. The slitting of the collapsed bubble may beproximate to a centerline of the collapsed bubble. The slit collapsedbubble may be separated into a first half-bubble and a secondhalf-bubble. The pre-selected partial width that is incrementallystretched may be centered approximately along the centerline of thecollapsed bubble. Each of the half-bubbles may include a fraction of thepre-selected partial width. Each fraction of the pre-selected partialwidth may extend from an edge of each collapsed half-bubble towards thecenterline of each collapsed bubble. Each fraction of the pre-selectedpartial width may be less than one-half of the width of eachhalf-bubble. Once stretched, each of the half-bubbles may be rolled ontoa separate master roll. Once the master roll is formed, it may be placedat the head end of a bag converting line to form drawstring trash bags.

In an alternative embodiment, two separate pre-selected widths of theabove-discussed collapsed bubble may be ring-rolled rather than a singlepre-selected width. Each of the two separate pre-selected widths may beoffset from the centerline of the collapsed bubble and offset from eachedge of the collapsed bubble.

The ring rolling of the incrementally stretched film may include thecollapsed bubble entering a pair of intermeshing rollers. Each of theintermeshing rollers may include a plurality of grooves perpendicular tothe axis of the rollers. The plurality of grooves on a first roller ofthe pair of intermeshing rollers may intermesh with the plurality ofgrooves on a second roller of the pair of intermeshing rollers. An axisof the first roller may be parallel to an axis of the second roller andthe axis of each roller may be perpendicular to the machine direction ofthe collapsed bubble. The pair of intermeshing rollers may incrementallystretch only a section or partial width of the collapsed bubble. Thecollapsed bubble may increase in overall width after passing through thepair of intermeshing rollers. Each intermeshing roller may rotate in adirection that the collapsed bubble is moving so that the collapsedbubble is drawn through the pair of intermeshing rollers. The ringrolling may also include a pair of spreading rollers downstream from thepair of intermeshing rollers. The axis of the spreading rollers may beparallel to each other and perpendicular to the machine direction of thecollapsed bubble. The pair of spreading rollers may maintain tension inthe collapsed bubble and spread out the overall width of the collapsedbubble after being stretched by the pair of intermeshing rollers.

In another embodiment of the present invention, bags may be formed froma polymeric film by a blown film extrusion process. The blown filmextrusion process may form a polymeric film tube. The polymeric filmtube may be collapsed to form a collapsed bubble and the collapsedbubble may have a collapsed bubble width extending from a first edge toa second edge of the collapsed bubble. The collapsed bubble may beseparated into a first half-bubble and a second half-bubble by aslitting operation. The first half-bubble may be rolled onto a firstmaster roll and the second half-bubble may be rolled onto a secondmaster roll. The first master roll may be fed into the front or head endof a bag converting line. Prior to converting the first master roll intobags, a portion of the collapsed bubble may be ring rolled. The ringrolling may be centered along a centerline of the first half-bubble. Thering rolled portion may comprise a partial width of the firsthalf-bubble and extend from a first edge of the first half-bubble towardand opposite second edge of the first half-bubble. The partial width ofthe first half-bubble may have a length that is less than half of awidth of the first half-bubble.

In a further embodiment of the invention, polymeric bags may be formedby a blown film extrusion process. The blown film extrusion process mayform a polymeric film tube. Once the polymeric film tube is formed, itmay be collapsed by a pair of nip rollers to form a collapsed bubble.The collapsed bubble may have a first edge and a second edge, bothextending along a length of the collapsed bubble, a distance between thefirst and the second edge defining a width of the collapsed bubble. Thecollapsed bubble may be slit along the first edge. A portion of a widthof the collapsed bubble may be ring-rolled to form an incrementallystretched portion. The incrementally stretched portion may form anincrementally stretched partial width that may be centered along acenterline of the collapsed bubble. The incrementally stretched partialwidth, in the alternative, may extend adjacent from the first side edgeof the collapsed bubble towards the second side edge of the collapsedbubble. The incrementally stretched partial width may have a width lessthan half the width of the collapsed bubble. Once the collapsed bubbleis incrementally stretched, it may feed into a bag converting operationand formed into bags. The ring rolling may be performed synchronouslywith the forming of the polymeric film tube and the forming of the bags.

In an additional embodiment of the invention, a bag may be formed frompolymeric film from a collapsed polymeric bubble formed from a blownfilm extrusion process. The bag may include a front panel and a backpanel. The front panel and back panel may be generally joined along afirst side edge, a second side edge, and a bottom edge of the respectivefront panel and back panel. The front panel may have a distal edgeopposite the bottom edge. The distal edge of the front panel may resultfrom the folded over portion of the front panel. The distal edge of thefront panel may provide a first hem and a first overlap area immediatelybelow the first hem. A drawstring may be encapsulated within the firsthem. The top of the hem may define an upper opening of the polymericbag. The first overlap area may comprise at least two layers ofpolymeric film below the first hem. The at least two layers of polymericfilm of the first overlap area may be sealed together by a lower seal.The first overlap area may fail to include a drawstring. The first hemand the first overlap area may comprise an incrementally stretchedpartial width of the collapsed bubble. The incrementally stretchedpartial width of the collapsed bubble may be incrementally stretchedsynchronously with the blown film extrusion process that forms thecollapsed bubble. The at least two layers of polymeric film of the firstoverlap area immediately adjacent or proximate to the first lower sealmay comprise un-stretched polymeric film.

BRIEF DESCRIPTION OF THE RELATED DRAWINGS

A full and complete understanding of the present invention may beobtained by reference to the detailed description of the presentinvention and certain embodiments when viewed with reference to theaccompanying drawings. The drawings can be briefly described as follows.

FIG. 1 provides a side view of a first embodiment of the presentinvention.

FIG. 2 provides a partial perspective view of the first embodiment shownin FIG. 1.

FIG. 3 provides a perspective view of a pair of intermeshing rollersutilized in the first embodiment.

FIG. 4 is a cross-sectional view of the intermeshing rollers taken alongcircle 4-4 of FIG. 3.

FIG. 5 is a partial perspective view of a second embodiment of thepresent invention.

FIG. 6 is a perspective view of a third embodiment of the presentinvention.

FIG. 7 is a perspective view of a fourth embodiment of the presentinvention.

FIG. 8 is a perspective view of a fifth embodiment of the presentinvention.

FIG. 9 is a partial top view of a ring rolled collapsed bubble of thepresent invention.

FIG. 10 is a perspective view of a sixth embodiment of the presentinvention.

FIG. 11 is a partial cross-sectional view of the sixth embodiment asshown in FIG. 10.

FIG. 12 is front view of the embodiment shown in FIG. 10 and FIG. 11.

FIG. 13 is a partial detailed front view of a seventh embodiment of thepresent invention.

FIG. 14 is a front view of an eighth embodiment of the presentinvention.

FIG. 15 is a front view of a ninth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present disclosure illustrates several embodiments of the presentinvention. It is not intended to provide an illustration or encompassall embodiments contemplated by the present invention. In view of thedisclosure of the present invention contained herein, a person havingordinary skill in the art will recognize that innumerable modificationsand insubstantial changes may be incorporated or otherwise includedwithin the present invention without diverging from the spirit of theinvention. Therefore, it is understood that the present invention is notlimited to those embodiments disclosed herein. The appended claims areintended to more fully and accurately encompass the invention to thefullest extent possible, but it is fully appreciated that certainlimitations on the use of particular terms are not intended toconclusively limit the scope of protection.

FIG. 1 provides a side view of a first embodiment of the presentinvention while FIG. 2 provides a perspective partial view of the sameembodiment. The first embodiment is a process for forming two sectionsof an incrementally stretched split polymeric film tube. The polymerictube is divided lengthwise into two sections and rolled onto two masterrolls. The polymeric film tube, which may also be referred to as abubble, is formed by a blown film extrusion process.

The blown film extrusion process begins by molten polymeric resin beingextruded through an annular die to form a bubble or tube of moltenpolymeric film 104. The direction that the film is extruded out of thedie is commonly referred to as the machine direction. The direction ofextrusion may also be referred to as the lengthwise direction of thebubble or polymeric film tube 104. Hence, the length of the polymerictube 104 extends parallel with the machine direction. The directiontransverse to the machine direction is commonly referred to as the crossdirection. The blown film extrusion process is well known in the art andis further explained in U.S. Pat. No. 7,753,666, which is herebyincorporated by reference in its entirety.

The polymeric resin used in the blown film extrusion process may vary.However, for forming polymeric bags, a polyethylene resin is commonlyused. In the current state of the art for polymeric bags, a blend ofvarious polyethylene polymers may be used. A polymer blend can havelinear low-density polyethylene (LLDPE) as the primary component, butother polymers may be utilized including, but not limited to, otherpolyethylene resins such as high-density polyethylene (HDPE) orlow-density polyethylene (LDPE). Typically, the primary component of thepolymer blend, such as linear low-density polyethylene (LLDPE), willcomprise at least 75% of the polymer blend. The remaining portion of thepolymer blend may include additives including, but not limited to,coloring additives, anti-blocking agents, and/or odor control additives.

As shown in FIG. 1, once the bubble 104, or polymeric tube, of moltenfilm solidifies, the bubble 104 is collapsed by a pair of nip rollers108, which results in a collapsed bubble 110. The collapsed bubble 110includes two opposing interconnected surfaces of film extendingcontinuously in a lengthwise direction. As shown in FIG. 2, oncecollapsed, the collapsed bubble 110 has a first edge 112 and second edge114 defined in the opposing edges of the collapsed bubble 110 extendingthe length of the collapsed bubble 110. The distance from the first edge112 to the second edge 114 of the collapsed bubble 110 can define awidth of the collapsed bubble. The nip rollers 108 are commonly elevatedabove the extruder 106 a considerable distance, since the molten bubble104 is air-cooled and requires a relatively large vertical distance tocool and solidify before the bubble 104 is collapsed. Once the collapsedbubble 110 returns from the cooling tower (not shown), the collapsedbubble 110 can feed directly into a ring-rolling operation 120. As shownin FIG. 1 and more clearly in FIG. 2, the ring rolling operation 120 canbe configured to stretch only a portion of the width of the collapsedbubble 110. The ring rolling operation can include a pair ofintermeshing rollers 122 a, 122 b and a pair of spreading rollers 124 a,124 b.

As shown in FIGS. 3 and 4, the pair of intermeshing rollers 122 a, 122 bhas a plurality of grooves 128 a, 128 b and corresponding concentricrings formed perpendicular in relation to the axis of the intermeshingrollers 122 a, 122 b. The pair of intermeshing rollers 122 a, 122 b canbe arranged with the axis of each roller parallel to each other andperpendicular to the machine direction of the collapsed bubble 110. Thepair of intermeshing rollers 122 a, 122 b rotates in opposite directionsfrom each other, as shown in FIG. 3, so that the collapsed bubble 110 isdrawn through the pair of intermeshing rollers 122 a, 122 b. The tensionin the collapsed bubble 110 is maintained after passing through theintermeshing rollers 122 a, 122 b by a pair of spreading rollers 124 asshown in FIGS. 1 and 2. The spreading rollers 124 ensure that thecollapsed bubble 110 spreads evenly over its width and maintains theappropriate amount of tension in the collapsed bubble 110. The spreadingrollers 124 are typically arranged with each axis parallel to each otherand perpendicular to the machine direction of the collapsed bubble 110.

As shown in FIGS. 1 and 2, once the collapsed bubble 110 passes into thenip 126 of the pair of intermeshing rollers 122 a, 122 b, the collapsedbubble 110 is deformed by the plurality of grooves 128 a, 128 b and isstretched by a factor of a draw ratio. The draw ratio is a ratio betweenthe path-length that the plurality of grooves 128 a, 128 b causes thefilm to take versus the original length of the film width passed throughthe plurality of grooves 128 a, 128 b, as illustrated in FIG. 4. Sincethe collapsed bubble 110 enters the intermeshing rollers 122 a, 122 btravelling in the machine direction, the intermeshing rollers 122 a, 122b incrementally stretch the collapsed bubble 110 in the crossdirection—transverse to the machine direction.

As shown in FIG. 4, the film of the collapsed bubble 110 is stretched inbetween each groove of the plurality of grooves 128 a, 128 b, whichresults in a pattern of stretched and un-stretched lengths extendingalong the length of the collapsed bubble 110. Examined closely, thispattern of stretched and un-stretched lengths results in a pattern ofparallel thick ribs (un-stretched lengths) and thin ribs (stretchedlengths) extending in the machine direction of the collapsed bubble 110.In one particular embodiment, the spacing of the grooves can be 20grooves per inch, with each groove leading to a matching thin rib/thickrib extending along the length of the collapsed bubble 110. The spacingof the ribs in the film after stretching is greater than the groovespacing of the intermeshing rollers 122 a, 122 b, since the stretchingcauses each rib to spread away from each other. The pattern of thick andthin ribs is represented by a pattern of parallel and adjacent lines inthe figures. The spacing between ribs is exaggerated for ease ofillustration.

Once the collapsed bubble 110 has been incrementally stretched in thecross direction, the collapsed bubble 110 can be slit to form twoseparate partial collapsed bubbles 110 a and 110 b. As shown in FIGS. 1and 2, the slitting operation 140 of the collapsed bubble 110 can occurapproximately at a location between the first edge 112 and second edge114 of the collapsed bubble 110. A centerline can be defined to extendparallel to the length of the collapsed bubble and at the center of thecollapsed bubble 110, relative to the first edge 112 and second edge114. The centerline of the collapsed bubble 110 is also parallel to thefirst edge 112 and second edge 114. The slitting operation 140 can belocated approximately at the centerline of the collapsed bubble 110.Once the collapsed bubble 110 is slit at the centerline, it can beseparated into two half-bubbles 110 a, 110 b and each half-bubble can berolled onto separate master rolls 134 a, 134 b. The first half-bubble110 a can have a first edge 112 a and a second edge 112 b, the secondedge 112 b formed from the splitting operation 140. The secondhalf-bubble 110 b can have a first edge 114 a and a second edge 114 b,the second edge 114 b formed from the splitting operation 140.

As shown in FIGS. 2 and 3, the plurality of grooves 128 a, 128 b, can becentered along the centerline of the collapsed bubble 110. Hence, thering rolling operation 120 results in a first incrementally stretchedpartial width 116 centered about the width of the collapsed bubble 110.After the collapsed bubble 110 is split into a first and second halfbubbles 110 a, 110 b, the first incrementally stretched partial width116 of the collapsed bubble 110 results in a second incrementallystretched partial width 116 a of the first half-bubble 110 a and a thirdincrementally stretched partial width 116 b of the second half-bubble110 b. The second and third incrementally stretched partial widths 116a, 116 b extend from one of the second edges 112 b, 114 b of eachhalf-bubble 110 a, 110 b, towards one of the first edges 112 a, 114 a ofeach half-bubble 110 a, 110 b. In at least one embodiment, the secondand third incrementally stretched partial widths 116 a, 116 b, can havea width that is less than half the width of each half-bubble 110 a, 110b.

In one particular example, the collapsed bubble 110 may have a widthprior to stretching of 60 inches. The plurality of grooves 128 a, 128 bof the intermeshing rollers 122 a, 122 b may have a width ofapproximately 16 inches and a depth of engagement so that the 16 inchesof the collapsed bubble 110 that is engaged by the intermeshing rollers122 a, 122 b is stretched to approximately 20 inches. Thus, oncestretched, the width of the collapsed bubble 110 is approximately 64inches. Once the collapsed bubble 110 is separated into a firsthalf-bubble 110 a and a second half-bubble 110 b, each half bubble 110a, 110 b has an overall width of approximately 32 inches with anincrementally stretched partial width 116 a, 116 b of approximately 10inches.

As shown in FIGS. 1 and 2, each operation, including the blown filmextrusion and incremental stretching of the collapsed bubble 110 can beperformed synchronously. For example, at the same time a portion of thebubble 104 is being formed by the extruder 106, the same bubble 104, inthe form of a collapsed bubble 110, can be incrementally stretched bythe intermeshing rollers 122 a, 122 b.

Once each incrementally stretched collapsed half-bubble 110 a, 110 b hasbeen rolled onto a master roll, each master roll 134 a, 134 b can thenbe used to manufacture polymeric bags, including drawstring trash bags.One particular type of drawstring trash bag that the present inventionis particularly well suited for use is an extended hem drawstring trashbag, which is explained in greater detail below.

The collapsed bubble 110 can be stretched in other locations other thanabout the centerline of the collapsed bubble 110 as shown in FIG. 2.FIG. 5 shows use of incremental stretching to form two discrete widths,a first incrementally stretched partial width 118 a, and a secondincrementally stretched partial width 118 b of the collapsed bubble 110.Each incrementally stretched partial width 118 a, 118 b extends adjacentfrom the centerline of the collapsed bubble 110 towards one of the twoedges 112, 114 of the collapsed bubble 110.

As further shown in FIG. 5, after being incrementally stretched, thecollapsed bubble 110 can be separated by splitting operation 140 into afirst half-bubble 110 a and a second half bubble 110 b. The firsthalf-bubble 110 a has a first edge 112 a and a second edge 112 b. Thesecond half-bubble 110 b also has a first edge 114 a and a second edge114 b. The splitting operation 140 results in the first incrementallystretched partial width 118 a on the first half-bubble 110 a and thesecond incrementally stretched partial width 118 b on the secondhalf-bubble 110 b. Each incrementally stretched partial width 118 a, 118b is bounded by un-stretched material on both the first edge 112 a, 114a and the second edge 112 b, 114 b. Each half-bubble 110 a, 110 b can berolled onto a separate master roll 134 a, 134 b.

In one particular example, each incrementally stretched partial width118 a, 118 b can be incrementally stretched approximately 14 inches wideafter stretching, and have approximately a 12 inch width prior tostretching. The width of each half-bubble 110 a, 110 b, can beapproximately 29 inches prior to stretching and 31 inches afterstretching. The un-stretched material that bounds each side of eachincrementally stretched partial width 118 a, 118 b can varyconsiderably, but in one particular example, the width of eachun-stretched area can be approximately 8.5 inches.

As shown in FIG. 6, in another embodiment of the present invention, acollapsed bubble 110 is incrementally stretched a partial widthsynchronously with the extrusion of the bubble 104 and the converting ofthe collapsed bubble 110 into polymeric bags 200. Polymeric resin isfirst extruded from extruder 106 to form a polymeric tube or bubble 104.After being collapsed by nip rollers 108, the collapsed bubble 110 canbe slit on a first edge 112 of the collapsed bubble 110 by a slittingoperation 150. In an alternative embodiment, the slitting operation 150can be performed further downstream after the collapsed bubble 110 hasbeen incrementally stretched. The slitting mechanism cuts a first edge112 of the collapsed bubble 110 so that the collapsed bubble is open atthe first edge 112. The slitting operation 150 results in a first paneland a second panel from the two opposing faces of the collapsed bubble110 with each panel having a distal end at the first edge 112 and aninterconnected end at the second edge 114 of the collapsed bubble 110.

After being slit along the first edge 112, the collapsed bubble 110 canenter a pair of intermeshing rollers 122 a, 122 b through the nip 126.The intermeshing rollers 122 a, 122 b can have intermeshing grooves 128a, 128 b along only a partial width of the rollers, so that thecollapsed bubble 110 is incrementally stretched only along a portion ofits width to form an incrementally stretched partial width 116. Theintermeshing rollers 122 a, 122 b can engage the collapsed bubble 110from the first edge 112 to a certain distance inward from the first edge112. Once the collapsed bubble 110 is incrementally stretched, it canenter a bag converting operation 130 that converts the incrementallystretched collapsed bubble 110 into a plurality of trash bags 200. Thebag converting operation 130 can separate each panel of the collapsedbubble 110 and fold in half the incrementally stretch partial width 116of each panel towards the second edge 114 to form a pair incrementallystretched extended hems 246, 248 on each trash bag 200.

In one particular embodiment, the entire width of the collapsed bubble110 of FIG. 6 may be approximately 30 inches and the incrementallystretched partial width 116 may be approximately eight inches before thering rolling operation completes. After stretching, the incrementallystretched partial width 116 may grow to approximately 10 inches so thatthe overall width of the collapsed bubble 110 increases to approximately32 inches. After folding one-half of the incrementally stretched partialwidth 116 to form the pair of extended hems 246, 248, trash bags 200 maybe formed with each trash bag having a final length of approximately 27inches and each extended hem 246, 248 having a length of approximately 5inches.

In a further embodiment as shown in FIG. 7, a method of formingpolymeric bags can begin with a previously slit collapsed half-bubble110 a rolled onto a master roll 136. The collapsed half-bubble 110 a onthe master roll 136 can have previously been formed in a blown filmextrusion process. In this embodiment, the collapsed half-bubble 110 ais not incrementally stretched prior to being rolled onto the masterroll 136. The collapsed half-bubble 110 a is unrolled from the masterroll 136 and enters the nip 126 of the pair of intermeshing rollers 122a, 122 b. The intermeshing rollers 122 a, 122 b incrementally stretchthe collapsed half-bubble 110 a. The collapsed half-bubble 110 a isincrementally stretched only a partial width of the collapsedhalf-bubble 110 a. In this embodiment, the incrementally stretchedpartial width 116 extends from the second edge 112 b of the collapsedhalf-bubble 110 a towards the center of the collapsed half-bubble 110 awith a length less than half of the width of the collapsed half-bubble110 a. Once the collapsed half-bubble 110 a passes through thestretching rollers 124, it enters the bag converting operation 130.

During the bag converting operation 130 shown in FIG. 7, the slit on thesecond edge 112 b of the collapsed half-bubble 110 a provides a firstpanel and second panel from the collapsed half-bubble 110 a, each panelhaving a distal edge at the second edge 112 b. Each distal edge of eachpanel is folded inwards towards itself. The length of each fold isapproximately half of each incrementally stretched partial width 116.After being folded, an extended hem 246, 248 is defined in the collapsedhalf-bubble 110 a with the extended hem 246, 248 comprised of theincrementally stretched partial width 116. Prior to or during thefolding operation, a drawstring can be inserted adjacent to the foldwithin the folded area. To complete the bag converting operation 130,side seals and perforations are formed at pre-defined lengths extendingalong the width of the collapsed half-bubble 110 a.

In one particular example of the FIG. 7 embodiment, the entire width ofthe collapsed half-bubble 110 a may be approximately 30 inches and theincrementally stretched partial width 116 may be approximately eightinches before being stretched. After stretching, the incrementallystretched partial width 116 may grow to approximately 10 inches so thatthe overall width of the collapsed bubble 110 a increases toapproximately 32 inches. When converted to trash bags 200, thesedimensions results in trash bags 200 with a length of approximately 27inches and having approximately 5 inch long extended hems 246, 248.

In another embodiment shown in FIG. 8, a method of forming polymericbags can begin with a previously slit collapsed half-bubble 110 a rolledonto a master roll 136 as previously described regarding FIG. 7. Ratherthan incrementally stretching the collapsed bubble 110 a proximate tothe second edge 112 b, a partial width 118 of the half-bubble 110 a canbe incrementally stretched about the centerline of the half-bubble 110a. As shown in FIG. 8, the incrementally stretched partial width 118 isbounded on both sides by a partial width of un-stretched material of thehalf-bubble 110 a.

In one particular example, the incrementally stretched partial width 118can be approximately 17 inches prior to stretching and approximately 21inches after stretching. The un-stretched width adjacent to the secondedge 112 b can be approximately 6 inches and the un-stretched widthadjacent to the first edge 112 a can be approximately 2 inches. Theentire width of collapsed half-bubble 110 a can be approximately 26inches prior to stretching and approximately 29 inches after stretching.

After being incrementally stretched, the collapsed half-bubble 110 a canthen enter a bag converting operation 130. In the bag convertingoperation 130, the collapsed bubble can be converted into a plurality ofdrawstring trash bags 200 as previously discussed. However, for theembodiment shown in FIG. 8, the hem of each drawstring trash bag is notformed from incrementally stretched material but rather un-stretchedmaterial. Furthermore, the hem can be formed from less width of thecollapsed bubble than the embodiment of FIG. 7. For instance, in oneparticular embodiment, four inches of the collapsed bubble along thesecond edge 112 b can be used to form a resulting hem with a two-inchlength after being folded.

Shown in FIG. 9 is an alternative embodiment of a partiallyincrementally stretched collapsed half-bubble 110 a. The half-bubble 110a can be formed in the same manner as described for the embodimentsshown in either FIG. 5 or FIG. 8 but with the location of where theplurality of grooves 128 a, 128 b of the intermeshing rollers 122 a, 122b engage the collapsed bubble offset from the previous embodiments. Asshown in FIG. 9, the incrementally stretched partial width 138 islocated adjacent to the second edge 112 b of the half-bubble 110 a witha partial width of un-stretched film 142 separating the incrementallystretched partial width 138 from the second edge 112 b. The width of theincrementally stretched partial width 138 can be limited so that morethan half of a width un-stretched material of the half-bubble 110 aseparates the incrementally stretched partial width 138 from the firstedge 112 a. The partial width of un-stretched film 142 can have a widththat is a fraction, less than one-half, of the width of theincrementally stretched partial width 138.

In a particular embodiment of the FIG. 9 embodiment, after stretching,the entire width of the collapsed bubble 110 or half-bubble 110 a can beapproximately 32 inches. The incrementally stretched partial width 138can be approximately nine inches after stretching, the un-stretchedregion between the incrementally stretched partial width 138 and firstedge 112 can be approximately one inch, and the remaining un-stretchedwidth of the collapsed bubble can be approximately 22 inches.

As previously discussed, the previously disclosed embodiments of theinvention are particularly well adapted for use in an extended hemdrawstring trash bag. FIG. 10 provides a perspective view, FIG. 11provides a top cross-section view, and FIG. 12 provides a front view ofsuch a trash bag. Looking collectively at FIGS. 10-12, the extended hemdrawstring trash bag 200 is comprised of a front panel 202 and a backpanel 204, the front panel 202 and back panel 204 being substantiallyrectangular in shape and joined along a first edge 210, a second edge212, and a bottom edge 214 to provide the body of the bag. The frontpanel 202 and back panel 204 may be formed from a single piece ofpolymeric film, such as a section of the collapsed bubble 110 orcollapsed half-bubble 110 a, 110 b. The bottom edge 114 of the collapsedbubble 110 can form the bottom edge 214 of the trash bag 200. Thesection of the collapsed bubble 110 is subsequently sealed along thefirst edge 210 and second edge 212 of the trash bag.

In FIG. 11, a cross-sectional partial view of the extended hemdrawstring trash bag 200 is shown. In particular, an upper cross-sectionof a drawstring trash bag 200 is depicted, although the thicknesses anddimensions are exaggerated to better illustrate the relation between thevarious parts of the bag. During manufacture of the bag, the distal edge216 of the front panel 202, i.e. the edge of the folded-over portion ofthe front panel 202 results from the fold-over portion defining thefirst hem 222 in the front panel 202 and a first drawstring 232 disposedwithin the first hem 222. Similarly, the distal edge 218 of the backpanel 204 results from the fold-over portion defining the second hem 224with a second drawstring 234 disposed in the second hem 224. The upperboundaries of the hems 222, 224 define the upper opening 220 of thedrawstring trash bag 200.

The drawstrings 232, 234 may be comprised of traditional high-densitypolyethylene drawstrings or, in some embodiments, elastic orelastic-like polymeric components. The drawstrings 232, 234 are anchoredto the front panel 202 and back panel 204 at the ends of the respectivedrawstrings 232, 234 near the first side edge 210 and second side edge212. In particular, the drawstrings 232, 234 are commonly anchored usingshort seals 236, 238 as shown in FIGS. 10 and 12, the short seals 236,238 fusing both drawstrings 232, 234 with both the front panel 202 andthe back panel 204. Other than the anchor point, the drawstrings 232,234 are generally loose within the hems 222, 224 enabling thedrawstrings 222, 224 to be accessed and pulled through the respectivedrawstring cutouts 226, 228 centrally located between the first sideedge 210 and second side edge 212. Consequently, when the drawstrings232, 234 are pulled through the drawstring cutouts 226, 228 of thedrawstring trash bag 200, the respective upper corners of the drawstringtrash bag 200 are pulled together to facilitate closure of the bag.

Now looking at FIGS. 10-12, the distal edges 216, 218 of the respectivefront and back panels 202, 204 are located a distance below therespective hems 222, 224. Thus, the front panel 202 has an overlap area242 that extends from the lower boundary of the first hem 222 to thedistal edge 216 of the front panel 202. In the same manner, the backpanel 204 has an overlap area 244 that extends from the lower boundaryof the second hem 224 to the distal edge 218 of the back panel 204.

Thus, for the front panel 202, the overlap area 242 comprises two layersof polymeric film, and the hem overlap area 244 of the back panel 204also comprises two layers of polymeric film according to the depictedembodiment. The length of the first overlap area 242 and the secondoverlap area 244 can be selected to be any length including a distanceending only slightly below the bottom boundaries of the respective hems222, 224 or a distance that extends nearly to the bottom of the bag. Thearea of the first hem 222 and overlap area 242 defines a first extendedhem area 246. In a likewise manner, the area of the second hem 224 andthe overlap area 244 defines a second extended hem area 248.

When utilizing the above-described methods of incremental stretching,the extended hem areas 246, 248 may be comprised of the partiallyincrementally stretched width 116, 116 a, 116 b, or 138 of FIG. 2, 6, 7,or 9, depending upon the method utilized to form the incrementallystretched width.

The drawstring trash bag depicted in FIGS. 10-12 is illustrated ashaving hem seals 262, 264 extending across the width of the drawstringtrash bag 200. Additionally, lower seals 272, 274 are provided in therespective panels 202, 204 proximate to the respective distal edges 216,218. By providing hem seals 262, 264 near the top of the overlap areas242, 244 and lower seals 272, 274 near the bottom of the overlap areas242, 244, the two layers of polymeric film comprising each overlap area242, 244 are kept in close proximity, providing effectively a two-plypolymeric film of increased thickness in the region of the overlap areas242, 244.

The overlap areas 242, 244, as shown in the depicted embodiments,provide important benefits during use of the drawstring trash bag 200.The primary benefit offered by the overlap areas 242, 244 is reinforcingthe drawstring trash bag 200 in the areas immediately below the hems222, 224 and drawtape 232, 234. As best illustrated by FIG. 11, it canbe seen that the thickness of the polymeric film is increasedsubstantially in the overlap areas 242, 244 compared to the remainingarea of the front panel 202 and back panel 204 below the overlap areas242, 244. The thicker overlap area 242, 244 is therefore expected to bestronger than the remainder of the bag. Thus, in the event that aconsumer is carrying the bag or gripping the bag in one or both of theoverlap areas 242, 244, it is less likely that the drawstring trash bag200 will puncture or tear in that particular area. By reducing thelikelihood that the drawstring trash bag 200 will fail when a consumergrabs the drawstring trash bag 200 in the overlap areas 242, 244, thedrawstring trash bag 200 is more useful—especially when it containsheavier items or debris.

For example, in the case of a collapsed bubble 110 or collapsedhalf-bubble 110 a, the film of the bubble can have a nominal thicknessof 0.7 mil. The incrementally stretched partial width 116 or 116 a ofFIG. 2, 6, 7 can have a width of 10 inches with an average stretch of 20percent, which leads to approximately an average thickness of 0.56 milfor the incrementally stretched partial width 116 or 116 a. Theincrementally stretched collapsed bubble 110 or collapsed half-bubble110 a can be formed into extended hem trash bags 200 with theincrementally stretch partial width 116, 116 a formed into the extendedhem areas 246, 248. The resulting average thickness of each extended hemareas 246, 248 can be approximately 1.12 mil, with each extended hemarea 246, 248 having a length of approximately 5 inches. Thus, theextended hem areas 246, 248 may provide an increase in overall filmthickness and hence strength while not utilizing as much material aswould be required from film that had not been partially incrementallystretched.

If the extended hem areas 246 and 248 were composed of un-stretchedfilm, then the thickness of the extended hem areas would be double inrelation to the remaining body of the bag. Although this would beexpected to provide for a substantial increase in the strength of theextended hem area of the bag, it also would substantially increase theamount of polymeric resin used to manufacture the bag. By forming theextended hem areas 246, 248 of the bag from film that has beenincrementally stretched, a substantial increase in strength is impartedto this area of the bag while decreasing the amount of material requiredto manufacture each bag in comparison to an extended hem bag notutilizing film that has been partially incrementally stretched.

The collapsed half-bubble 110 a of FIG. 9 can also be used to form anextended hem drawstring trash bag as shown in FIGS. 10-12. A detailedsectional view of this bag is shown in FIG. 13. To form the extended hemareas 246 and 248 of the trash bag, each panel of the collapsed bubble110 can be folded into itself a slight distance below a middle of theincrementally stretched partial width 138. Thus, the incrementallystretched partial width 138 encompasses a substantial portion of theextended hem areas 246 and 248. However, a bottom area of the extendedhem area 246 extending from the distal edge 216 and encompassing thelocation of the lower seal 272 is comprised of the partial width ofun-stretched film 142 of FIG. 9. This partial width of un-stretched film142 of FIG. 9 is shown in FIG. 13 extending from the distal edge 216 tothe border of the incrementally stretched partial width 276. In oneparticular example, a width of the un-stretched film 142 can beapproximately one inch.

Use of the incrementally stretched partial width 138 of FIG. 9 offersadditional advantages from other methods disclosed to form anincrementally stretched partial width. For instance, there is a riskthat incremental stretching of the film of the collapsed bubble couldinterfere with the sealing of the trash bag, such as for the lower seal272 of FIG. 13. Use of the incrementally stretched half-bubble 110 a ofFIG. 9 limits this risk since the film is not stretched at the locationof the lower seal 272. Thus, a more secure lower seal 272 may resultfrom this embodiment and lead to a stronger and more reliable trash bag.

FIG. 14 illustrates another extended hem drawstring trash bag utilizingan incrementally stretched partial width created via the methodspreviously described. The trash bag 200 shares many of the same featuresas the trash bag illustrated in FIGS. 10-12. Hence, likewise featuresshare the same identifiers as the previous figures. However, the bagillustrated by FIG. 14 utilizes incremental stretching in a differentarea of the bag from the previously illustrated bag of FIGS. 10-12.Rather than utilizing incremental stretching on the extended hemdrawstring trash bag in the extended hem areas 246, 248 of the trashbag, the bag body 250 is incrementally stretched. The processesdiscussed and shown for FIGS. 5 and 8 may be utilized to manufacture thebag shown in FIG. 14. This embodiment allows use of film with a thinneraverage gauge to be present in the bag body 250 for circumstances whereit is desirable for the extended hem areas 246, 248 to have greater thantwice the thickness of the bag body. The bag body 250 can be defined tobe the section of the front and back panel 202, 204 located below thelower seals 272, 274 and above the bottom edge 214.

In one particularly example for FIG. 14, the processes described abovecan form a collapsed bubble 110 or collapsed half-bubble 110 a having afilm thickness of approximately 0.8 mil. Thus, the total thickness ofeach extended hem area 246, 248 will be approximately 1.6 mil. However,if the 0.8 mil film is stretched on average 15 percent, the resultantaverage thickness of the incrementally stretched region of the bag bodywill be approximately 0.68 mils. In a particular embodiment, the lengthof the incrementally stretched region of the bag body 250 can beapproximately 18 inches with two inches of the bag body 250 on each sideof the incrementally stretched region left un-stretched. Thus, theentire length of the bag body 250 can be 22 inches. The extended hemarea of the bag can have a length of 5 inches so that the entire lengthof the bag 200 is approximately 27 inches.

A further embodiment of a drawstring trash bag is shown in FIG. 15 thatmay utilize the previously discussed methods of partial incrementalstretching of a collapsed bubble. The embodiment of FIG. 15 fails toinclude overlap areas 242, 244 and hence does not include an extendedhem area 246/248 as shown in FIG. 11. In this instance, the bag body 250is incrementally stretched to reduce the amount of film used in the bagbody 250. The processes discussed and shown for FIGS. 5 and 8 may beutilized to manufacture the bag shown in FIG. 15.

The amount of film used is limited in this embodiment since the hem isnot extended, relative to the embodiment shown in FIG. 14. Theembodiment of FIG. 15 allows the use of a thicker film than normallywould be used to increase the strength of the bottom of the bag and thehems 222, 224 of the bag. By utilizing one of the incremental stretchingmethods described above, the bag body 250 can be incrementally stretchedwhile the hems 222, 224 and the film immediately below the hems 222, 224can be left un-stretched so that the area proximate to the hems 222, 224has greater strength than the remaining area of the bag.

In one particular embodiment, the collapsed bubble film thickness can bea nominal thickness of one mil. A partial width of the collapsed bubble110 or collapsed half-bubble 110 a can be stretched approximately 20percent so that when the collapsed bubble 110 or collapsed half-bubble110 a is converted into bags, the bag body 250 comprises theincrementally stretched film. The resultant average thickness of the bagbody 250 that has been incrementally stretched can be approximately 0.8mil. For a trash bag with an overall length of approximately 27 inches,approximately 21 inches of the bag body can be incrementally stretchedwith approximately two inches of the bag bottom un-stretched, leavingapproximately a two-inch un-stretched hem, and approximately two inchesbelow the hem un-stretched. Thus, the bag 200 should have targetedincreased strength in the bag bottom and hem area, in comparison to abag made exclusively out of un-stretched 0.8 mil film.

As previously noted, the specific embodiments depicted herein are notintended to limit the scope of the present invention. Indeed, it iscontemplated that any number of different embodiments may be utilizedwithout diverging from the spirit of the invention. Therefore, theappended claims are intended to more fully encompass the full scope ofthe present invention.

I claim:
 1. A method of forming a master roll of polymeric film forforming trash bags, the method comprising: forming a polymeric film tubevia a blown film extrusion process, collapsing the polymeric film tubeto form a collapsed bubble, ring-rolling a partial width of thecollapsed bubble forming an incrementally stretched partial width,slitting the collapsed bubble lengthwise in proximity to the centerlineof the collapsed bubble, separating the slit collapsed bubble into afirst half-bubble and a second half-bubble, and rolling each half-bubbleonto a separate master roll.
 2. The method of claim 1 furthercomprising: the incrementally stretched partial width centeredapproximately along a centerline of the collapsed bubble whereinseparating the collapsed bubble results in each half-bubble having afraction of the incrementally stretched partial width.
 3. The method ofclaim 1 further comprising: placing the at least one master roll at thehead end of a bag converting line for forming drawstring trash bags. 4.The method of claim 1, the ring rolling further comprising: a pair ofintermeshing rollers, each roller including a plurality of groovesperpendicular to the axis of each roller, the plurality of grooves oneach roller intermeshing with each other, the axis of each rollerparallel to each other, each intermeshing roller rotating in a directionthat the collapsed bubble is moving so that the bubble is drawn throughthe pair of intermeshing rollers, and a pair of spreading rollersdownstream from the pair of intermeshing rollers that maintain tensionin the collapsed bubble and spreads the overall width of the collapsedbubble after being stretched by the pair of intermeshing rollers.
 5. Amethod of forming bags from a polymeric film, the method comprising:forming a polymeric film tube via a blown film extrusion process,collapsing the polymeric film tube to form a collapsed bubble,separating the collapsed bubble into a first half-bubble and a secondhalf-bubble, rolling the first half-bubble onto a first master roll andthe second half-bubble onto a second master roll, placing and feedingthe first master roll at a front of a bag converting line, ring rollinga portion of the first half-bubble to form a ring rolled portion, andforming bags from the ring rolled first half-bubble.
 6. The method ofclaim 5 wherein the ring rolling is centered along a centerline of thefirst half-bubble.
 7. The method of claim 5 further comprising: the ringrolled portion extending from a first edge towards an opposite secondedge of the first half-bubble.
 8. The method of claim 7 wherein the ringrolled portion is less than half a width of the first half-bubble. 9.The method of claim 5, the ring rolling further comprising: a pair ofintermeshing rollers, each roller including a plurality of groovesperpendicular to the axis of each roller, the plurality of grooves oneach roller intermeshing with each other, the axis of each rollerparallel to each other, each roller rotating in a direction that thefirst half-bubble is moving so that the first half-bubble is drawnthrough the pair of intermeshing rollers, and a pair of spreadingrollers downstream from the pair of intermeshing rollers that maintaintension in the first half-bubble and spreads the overall width of thefirst half-bubble after being stretched by the pair of intermeshingrollers.
 10. A method of forming polymeric bags, the method comprising:forming a polymeric film tube via a blown film extrusion process,collapsing the polymeric film tube to form a collapsed bubble, thecollapsed bubble having a first edge and a second edge opposite thefirst edge, ring-rolling a portion of a width of the collapsed bubbleforming a ring-rolled portion, slitting the collapsed bubble lengthwiseproximate to the first edge, feeding the collapsed bubble into a bagconverting machine, forming bags from the collapsed bubble.
 11. Themethod of claim 10 further comprising: the ring-rolling performedsynchronously with the forming of the polymeric film tube.
 12. Themethod of claim 10 further comprising: the ring-rolled portion definingan incrementally stretched partial width of the collapsed bubble, theincrementally stretched partial width centered approximately along acenterline of the collapsed bubble.
 13. The method of claim 10 furthercomprising: the ring-rolled portion defining an incrementally stretchedpartial width of the collapsed bubble, the incrementally stretchedpartial width extending from the first edge towards the second edge ofthe collapsed bubble.
 14. The method of claim 13 further comprising: theincrementally stretched partial width having a width less than half of awidth of the collapsed bubble.
 15. The method of claim 10, the ringrolling further comprising: a pair of intermeshing rollers, each rollerincluding a plurality of grooves perpendicular to an axis of eachroller, the plurality of grooves on each roller intermeshing with eachother, the axis of each roller parallel to each other, each rollerrotating in a direction that the collapsed bubble is moving so that thecollapsed bubble is drawn through the pair of intermeshing rollers, anda pair of spreading rollers downstream from the pair of intermeshingrollers that maintain tension in the collapsed bubble and spread theoverall width of the collapsed bubble after being stretched by the pairof intermeshing rollers.